In the roofing trades there are generally two types of roof surfaces. One is a pitched surface and the other a flat or commercial surface. In both situations, materials which are thin in nature are rigidly attached to the substrate, or deck. These thin materials are more commonly referred to as underlayments. Their primary function is to prevent water and vapor penetration into the structure proper. They are generally made from an organic mat which is saturated in a petroleum distillate. The underlayments usually come in three-foot rolls and are applied to the deck in horizontal courses starting at the eave or low point of the deck having each following course lap of the previous. When installed correctly, any moisture will wash over the courses and off the roof.
Due to the said thin nature of these underlayments, it would seem appropriate to have a designated fastener for the attachment of such to the roof deck. There are currently many fasteners used to apply underlayments to roof decks and indeed some even claim to be designated underlayment fasteners. However, as will be described, these and other fasteners not only do a poor job, they cause underlayment failure resulting in structural damage, and injury to the installer from sliding on loose material. The most common fastener used to secure an underlayment would be a shingle roofing nail. The head of this fastener is usually five-eighths in diameter and has a shank portion of one inch and better. The problem with this nail is it tends to "blow" through the underlayment due to the sheer force needed to install it. Subsequently, extra time and care are necessary to assure the nails are not puncturing the underlayment ultimately resulting in lost productivity. Also of concern is the poor lateral holding power of this nail. When walked upon, the only portion of the nail preventing the underlayment from tearing loose (on a pitched roof) is the gauge, or thickness of the nail shank itself. Such an occurrence did in fact take place causing injury to the worker as he slid off the roof. This was a compelling factor in designing the present invention. As further outlined, the above-mentioned nail, and others, provide very little holding power against the wind. In new construction structures with a pitched roof, it is common for the underlayment to be installed over the skeletal framework of the structure, sometimes weeks ahead of the shingles. This process is called a "dry-in" procedure. It allows the continuance of interior work in foul weather and provides a temporary water barrier. In many situations, the "dry-in" blows off after a few days due to the ineffective holding power of the aforementioned nail which results in damage to the structure from rain, additional materials, and extra labor to reinstall same. A final problem typically encountered by using shingle nails would be the many punctures left in the underlayment from them not seating into the deck properly. Many times the nail will abruptly alter its course while being driven in (if you hit a knothole or gap in the roof boards), thereby causing the head of the nail to make contact with the underlayment at such an angle as to cause the edge of the nail head to cut through the underlayment. The resulting aperture, left as is, will allow water to seep into the structure.
Another type of fastener found presently in the art is a one inch diameter "cap" nail. It basically provides better service due to increased size of the head. It holds better than the shingle nail in windy conditions. However, it still provides poor lateral holding power as again the only portion of the fastener preventing tear out is the shank, which is very thin. This type of fastener is primarily used to secure insulation board and base sheet materials to flat, or commercial, roof decks. However, it is used on pitched roofs as stated above. This fastener is more expensive than shingle nails, thereby prohibiting its widespread use on pitched roofs.
One other embodiment of the "cap" nail utilizes a one inch in diameter cap, or head, made of plastic. It has an ardox-type shank extending centrally through the slightly domed cap. It is used on underlayments and wall sheathings. When installed the dome flattens, thereby putting passive pressure against the underlayment binding it to the pitched roof deck. However, this fastener is not only more expensive than the present invention, it loses most of its holding power in direct sunlight and as the temperature increases. The thickness of the plastic head of this fastener is such that, in certain situations, they can hold up an area of the shingle preventing it from seating flatly to the roof deck.
There are other fasteners such as tacks and a multitude of staples which can be used to attach underlayments to a roof deck. Staples do not work as there is no way to adjust the impact which usually results in "blow" throughs, and violate some local building codes. Tacks are generally too small to hold the underlayment in windy conditions.
As can be understood by the problems outlined above, there is a real need for the present invention. The objectives of the present invention therefore will be to provide a roofing fastener having a greatly improved holding capability against wind uplift and lateral tear out. This improvement will therefore reduce the amount of fasteners needed per job.
Another objective of the present invention is to provide a fastener which can be produced at a lower cost than the prior art.
And still another objective of the present invention is to provide a multipurpose roofing and siding fastener which reduces the amount of punctures in the underlayment, thereby allowing the underlayment to withstand the weather for longer periods of time in a "dry-in" procedure.